1. Field of the Invention
The present invention relates to an internal pressure regulating system for a flexible bag body used for an inflatable and collapsible dam, particularly, to an internal pressure regulating system for a flexible bag body, in which an internal pressure of a flexible bag body can be automatically regulated, by a simple structure, in accordance with a level of a water area in which the flexible bag body is provided. The present invention also relates to a flexible membrane dam using the above-described system, and a method for regulating an internal pressure of the flexible membrane dam.
2. Description of the Related Art
Conventionally, a flexible membrane dam/weir has been widely used, wherein a flexible bag body is inflated by supplying air therein and is deflated by discharging air therefrom. Such a flexible membrane dam is structured in such a manner that a flexible bag body having a heightwise dimension corresponding to an operating condition is in advance prepared, and placed on the ground near a watercourse such as a river to form a collapsible dam.
There are cases in which due to an abnormal condition of an air supplying device or due to exposure to sunlight in a state in which the flexible bag body is inflated when a water area in which the flexible bag body is provided, has a low level, an internal pressure of the flexible bag body may excessively increase so that a tension exceeding an operating standard would act on the flexible bag body. Accordingly, heretofore, there have been used internal pressure regulating systems using a water sealing pipe, a U-tube, or a back pressure regulating valve.
FIGS. 4A and 4B show such conventional internal pressure regulating systems as described above. FIG. 4A is a cross sectional view when a water sealing pipe is used, and FIG. 4B is a cross sectional view when a U-tube is used. The water sealing pipe is structured in such a manner that an open end 12 of a branch pipe 11 into which gas within a flexible bag body (not shown) is introduced, is submerged in the water 13. When the internal pressure of the flexible bag body becomes a water head pressure or higher, gas within the flexible bag body pushes out water within the branch pipe 11 and leaks out so that the internal pressure of the flexible bag body decreases.
An internal pressure regulating system using a U-tube is structured in such a manner that water 15 is stored in a U-tube 14 into which gas within the flexible bag body is introduced, and when an internal pressure of the bag body increases, gas within the bag body pushes up the water 15 within the U-tube 14 so as to regulate the internal pressure and a water head pressure. Accordingly, the capacity of the flexible bag body increases by an amount of water pushed up, and the internal pressure decreases. Further, a back pressure regulating valve is provided in the flexible bag body, and when the internal pressure becomes a predetermined value or higher, the valve is brought into an open state.
However, in the internal pressure regulating systems using a water sealing pipe or a U-tube, suitable supply of water into the pipe is required and a special piping structure becomes necessary. Further, such internal pressure regulating systems using a water sealing pipe, a U-tube, or a back pressure regulating valve as described above are not necessarily sufficient ones in the structural and operational aspects, and each have a problem in that the internal pressure of the flexible bag body cannot be regulated in accordance with a level of a water area in which the flexible bag body is provided.
In view of the aforementioned, it is one object of the present invention to improve conventional internal pressure regulating systems to provide an internal pressure regulating system for a flexible bag body, which makes it possible not only to prevent an internal pressure of the flexible bag body from excessively increasing, but also to regulate, by a simple structure, the internal pressure in accordance with a level of a water area in which the flexible bag body is provided. Further, it is another object of the present invention to provide a flexible membrane dam which has a predetermined heightwise dimension by regulating an internal pressure thereof and which is deflated by a proper overflow, and a method for regulating an internal pressure of the flexible membrane dam.
The present invention has been devised in order to achieve the above-described objects. A first aspect of the present invention is an internal pressure regulating system for a flexible bag body, in which gas within a flexible bag body is discharged when the flexible bag body used for a collapsible dam is excessively pressurized, the system comprising a flexible bag body which can be inflated with a gas for damming the body of water into upstream and downstream regions, and a pipe body having opposite first and second ends, wherein the bag body includes an exhaust opening for exhausting the gas, the first end of the pipe body is connected to the exhaust opening in the bag body, and the second end of the pipe body is introduced into the upstream region of the body of water. Namely, due to utilization of the pressure of the water at the upstream side, the internal pressure of the bag body can be automatically adjusted so as to correspond to the upstream water level.
Preferably, an internal pressure regulating system for a flexible bag body is provided in which at least one non-return valve is provided in the pipe body to prevent water from flowing from the upstream side into the bag body.
More preferably, the open end of the pipe body is submerged in water, from the surface of the water at the upstream side of the water area in which the flexible bag body is placed, at a position which is lower than or equal to a reference level at which the flexible bag body is installed. The exhaust opening of the bag body is provided at a position separated from an air supplying opening at which gas from an air supplying device is supplied into the bag body, particularly, the exhaust opening is provided at one end of the bag body. The air supplying opening is provided at the other end of the bag body. Further, the exhaust opening is provided at an upper side of a level of drain within the bag body. Drain is produced by the condensation of the water content contained in the gas supplied into the bag body and a level of drain is an amount of drain collected at the base of the bag body.
A second aspect of the present invention is a flexible membrane dam including the above-described internal pressure regulating system, in which the flexible bag body can be inflated by supplying gas therein and can be deflated by discharging gas therefrom.
A third aspect of the present invention is a method for regulating an internal pressure in a flexible membrane dam, which includes continuously or intermittently supplying gas into a flexible bag body.
According to the internal pressure regulating system of the present invention, the internal pressure of the bag body is automatically adjusted so as to correspond to the upstream water level. That is, when an internal pressure higher than or equal to the upstream water level is generated in the bag body, air is blown off from the internal pressure regulating system. Further, in an overflow state, the internal pressure is adjusted so as to correspond to an overflow level. In a non-overflow state, air pressure is adjusted to become an internal pressure corresponding to the upstream water level, and excessive increase in the pressure caused by exposure to sunlight or the like is prevented. As described above, in the present invention, a mechanical structure in which the internal pressure can be safely adjusted in accordance with the upstream water level, is provided without using an electrical structure which may cause a failure.